ISSN: 1945-7545
Published Online: 31 August 2005
Page Count: 9

Triaxial Ultra-Small Strain Measurements Using Laser Interferometry

Heymann, G
Professor, University of Pretoria, Pretoria,

Clayton, CRI
Professor of Infrastructure Engineering, University of Southampton, Southampton,

Reed, GT
Professor of Optoelectronics, University of Surrey, Buildford,

(Received 6 March 2003; accepted 7 April 2005)

Abstract

This paper describes a prototype device for ultra-small strain triaxial stiffness measurement, using laser-optic interferometry, and based upon the Fabry-Perot principle. The results of a test on an intact specimen of weak rock are presented, and comparisons made between measurements using this device and a submersible LVDT system. The displacement resolution of the interferometer was 0.0006 μm and the strain resolution 8 × 10⁻⁷%. It is shown that the measurement uncertainty of the instrument was low compared with the magnitude of the displacements measured and in addition it was sufficiently accurate to detect the linear stress-strain behavior of a weak rock.

Keywords:
triaxial test, small strain stiffness, local strain instrumentation, laser interferometry

Paper ID: GTJ10406
DOI: 10.1520/GTJ10406
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